The thermal properties of materials can be characterized by a number of characteristics, such as thermal conductivity and thermal effusivity. Thermal conductivity is a measure of the ability of a material to conduct heat (W/mK). Thermal effusivity is defined as the square root of the product of thermal conductivity (W/mK) times the density (kg/m3) times heat capacity (J/kgK). Thermal effusivity is a heat transfer property that can indicate the interfacial temperature when two semi-infinite objects at different temperatures touch.
Thermal effusivity and thermal conductivity provide a quantitative measure of the thermal impedance of a region of material and a tool to test consistent quality on a film product. Thermal properties of sheet material usually depend on how the material is processed among other factors, and information related to the thermal properties can be helpful in developing new products. However, there are difficulties in measuring the thermal effusivity and/or thermal conductivity of very thin layers of sheet materials, especially very thin coatings on much thicker substrates.